We propose to study the stereoselective pharmacokinetics (absorption, distribution, metabolism and excretion) and pharmacology of d,l-methadone in man (addicts and other subjects), rats and in vitro preparations including isolated rat liver microsomes and the isolated perfused rat liver. A specific method using radiolabelled methadone will be developed to measure and separate methadone from its metabolites. The effect of one isomer on the rate of metabolism and pharmacological response of the other isomer will be investigated by combining the unlabelled levorotatory and dextrorotatory isomer and vice versa. Qualitative and quantitative changes in the metabolism of each isomer will be examined as a function of dose and response to other drugs such as phenobarbital, nalorphine, naloxone, SKF 525 A and nicotine. Separation, identification and quantitation of metabolites will be accomplished by countercurrent distribution, gas liquid chromatography and mass spectrometry. For the human studies three methods of analysis will be examined in order to resolve the racemates. The first is a highly novel approach which is currently in progress and involves stereospecific radioimmunoassay of each isomer, which we believe will be successful. The second is the derivatization of each enantiomer to form diastereoisomers, which can then be separated by gas chromatography. The third is the use of a stable isotope to distinguish and quantitate each isomer and/or its metabolites by mass spectrometry. The blood concentration of each isomer will be correlated with a) miosis, and b) other pharmacological effects in smokers and non- smokers. Stereospecific methods of analysis will be used to examine the metabolism of the racemate in tolerant and nontolerant subjects and relate this to dosage, use of other drugs, including other narcotics and narcotic antagonists, liver and kidney function, and plasma protein binding.